This invention relates to nail enamels. It particularly relates to nail enamels which are substantially free of the settling and the migration of the pigment and other materials suspended in the composition.
Conventional nail enamel compositions incorporate in their formulas a montmorillonite clay as a gellant to suspend pigments and pearlescent materials contained therein.
To achieve desired properties for these systems, as much as 2.0% or more of the gellant is recommended to effect complete and stable suspension. The use of larger amounts of the gellant in a nail enamel composition adversely affects the application and flow properties of the preparation. When the levels of the gellant are reduced to about 0.5-1.25%, other additives must then be added to maintain desired suspension and performance characteristics. It is also known that nail enamel compositions exhibit pigment migration, i.e., preferential separation, flocculation and flotation as distinguished from settling. While migration does not affect the performance of the nail enamel, the streaking effects noticeable from such migration are aesthetically undesirable.
U.S. Pat. No. 4,166,110 discloses a nail enamel which contains an organically substituted polysiloxane to render the enamel film easily strippable from the nail. The patent does not discuss how to incorporate pigments into such a formulation, and does not suggest coating pigments with the polysiloxane.
An article by B. V. Ashmead et al., "The Silicone Treatment of Titania", J. Oil Col. Chem. Assoc., Vol. 54 (1971), pp. 403-424, discusses the adsorption of various silicone polymers onto the surface of titanium dioxide and discloses that silicone treated pigments disperse better in coventional paint media than untreated pigments. This disclosure does not suggest how coated pigments would behave in the solvent system employed in nail enamels. Moreover, the emphasis on dispersion, i.e. the length of time one needs to stir the paint in order to disperse the pigment in the surrounding media, does not support any suggestion as to how quickly the pigment settles and/or migrates once stirring is stopped. Indeed, freedom from settling and migration is of little or no concern to paint manufacturers, because the paint is in a non-transparent can until the user opens the can, stirs the paint, and applies the paint. By contrast, freedom from settling and migration even without stirring are of vital concern to the nail enamel manufacturer, who customarily sells the enamel in a transparent bottle, because the customer must be persuaded to buy the enamel based on how the enamel looks in the bottle.